390 The American Gei)loyist, June, 1897 
slopes all the way up plentifully strewn with bowlders and 
fragments of Potsdam sandstone which must have been car- 
ried up by the ice from a northward or northeastward quar- 
ter.* This seems to indicate that the main ice-sheet over- 
rode the higher peaks at least for a time, and it seems to im- 
ply further that there was no considerable amount of vigor- 
ous glaciation by local glaciers of notable size or by a local 
ice-cap, either following the retreat of the main ice-sheet, and 
probably none preceding its advance. Such facts shed an 
important and very welcome light upon the climatic condi- 
tions that prevailed along the ice front. The}' show us that 
the peripheral belt of ablation on the surface of the ice-sheet 
must have been at least one hundred miles or more wide, (it 
may have been even three or four times this width) and hence 
that the neve line on the ice-sheet itself was well back front 
the front. For when the reentrant front of the ice-sheet rested 
against the northeast corner of the Adirondacks at an alti- 
tude of 1400 feet or over, the peneplain at 1400 to 1600 feet 
was distinctly below the snow or neve line. 
WHAT IS THE OLENELLUS FAUNA? 
By G:. F. Matthew, St. John. 
St. John, N. B., 23d March, I89T. 
Prof. N. H. Wincheli,, 
Dear Sir: — ^As you have reOiUested rtte to express in your journal my views as to 
what the Olenellus fauna is, and what its relation to Paradoxides, I have briefly 
outlined in the following article the data bearing on this point, known to me. I 
hope it may stimulate some of the American geologists to seek a polution of the prob^ 
lem that shall be more direct. In the great body of slates existing at lake Cham- 
plain and along the valley of the Hudson, with their enclosed limestone bands and 
lentil les. there must be faunal groups other than have been described, and the means 
of a better presentation of those already known. A careful search and mapping of 
exposures where fossils are found, would reveal the structure, and prove or disprove- 
the theory of the mingling of the Paradoxides and Olenellus faunas in the Hudson 
valley. 
Hoping that the following paper may meet your wishes, I remain 
Yours sincerely, 
GJ. F. Matthew. 
In view of the tendency that exists at the present time to 
refer all pre-paradoxidean faunas to the Olenellus horizon, 
* Stated by Prof. Hitchcock at Buffalo in August, 1896, in his report 
to the Geological Society of America on the peti'ographical excui-sion in 
the Adirondacks. 
